This invention relates to a liquid dispensing device for dispensing a precise, predetermined small quantity of liquid repeatedly therefrom and, more particularly to a liquid dispensing device of the kind including a housing adapted to be mounted on the top of a liquid container such as a bottle, a cylinder vertically mounted on the housing, a plunger slidably disposed in the cylinder with the upper end thereof projecting out of the upper end of the cylinder, a suction valve disposed in a passage to introduce liquid in the liquid container into the cylinder when the plunger moves upward in the cylinder, a discharge valve disposed in a passage to discharge liquid in the cylinder to the outside when the plunger moves downward in the cylinder, and means for restricting the upward movement of the plunger.
Various liquid dispensing devices of the aforementioned kind have been proposed as shown in e.g. U.S. Pat. Nos. 3574334, 3729022 and 3940027 or the like. However, there are shortcomings such that the construction is complicated thus increasing the manufacturing time and costs, a substantial portion of the device is fabricated of glassware thus having potential breakage, that it is difficult to thoroughly cleanse the dispenser, and it has been required to combine the dispenser with a liquid container having a particular size and the configuration. Further, to adjust the quantity of liquid dispensed from the dispenser there are usually provided a stop adjacent to the plunger to restricting the stroke thereof and, the position of the stop being adjustable along a scale, so that the quantity of the liquid can be changed for each time, however, the accuracy in the quantity will decrease, and in practical usage, it is usually required to reproducibly dispense desired definite quantities. Usually, it is sufficient to change the definite quantity between predetermined two or three quantities.
Further, the prior art dispensers have been generally objectionable in that it has been difficult to bleed air from the interior of the dispenser in starting the operation thus necessitating a plurality of strokes and, air bubbles remaining in the dispenser will results the error in the quantity of the liquid dispensed.